Prior art pressure-relief devices that relieve an over-pressure condition in a vessel or system are available.
Some pressure-relief devices, such as rupture disks, are one-time devices which that must be replaced after they are actuated. Other, so-called reclosable, pressure-relief devices automatically close when the overpressure condition is removed.
Until it is used a rupture disk will not leak when a vacuum is drawn within the vessel. However, the prior art reclosable pressure-relief device that employs a frusto-conical valve assembly or spherical valve assembly (which may include a resilient O-ring) has been found to leak under vacuum conditions.
Accordingly, it is believed that a reclosable pressure-relief device is needed which provides a seal adequate to maintain a vacuum when the vessel is evacuated.